Electric-furnace process.



PATENTED MAR. 3, 1908.

F. VON KUGBLGEN & G. 0. SEWARDQ ELECTRIC FURNACE PROCESS.

APPLIOATION FILED APR. 10. 1905.

2 SEEBTB-SHEET 1.

No. 880,743. PATENTED MARS, 1908. F. VON KUGELGEN & G. O. SE WARD.

ELECTRIC FURN AGE PROCESS.

APPLICATION FILED APR.10. 1906.

2 SHEETS-SHEET 2.

INVENTORS;

- E QWQ- By A [for/26315,

WITNESSES:

WM/j

UNITED STATES- PATENT OFFICE.

FRANZ VON KUGELGEN AND GEORGE O. SEWARD, OF HOLOOMBS ROCK, VIRGINIA, '7ASSIGNORS TO VIRGINIA LABORATORY COMPANY, OF NEW YORK, N. Y., A CORPO-RATION OF NEW YORK.

ELECTRIC-FURNACE PROCESS.

Specification of Letters Patent.

Patented March 3, 1908.

Application filed April 10. 1906. Serial No. 254.677.

. To all whom 'it may concern:

Be it known that we, FRANZ VON KI'FGEL- GEN, a subject of the German Emeror, and GEORGE O. SEWARD, a citizen of t e United States, bothresiding at Holcombs Rock, in the county of Bedford and Stateof-Virginia, have jointly invented certain new and useful Improvementsin Electric-Furnace Processes, of which the following is aspecification.

In our application No.243,494, filed J anuary 31, 1905, patented July 2,1907, No. 858,400 we have described a resistance furnace or anelectrolytic apparatus in which one or both of the electrodes is cooledby circulation of water therethrou h, which cooling permits thesubstitution 0 metal for carbon electrodes with certain advantagesspecified therein in detail, and which cooling may also be used toadvantage in connection with carbon electrodes.

The present application is in part taken from the previous ,a plication,and .is based on the application of the rocess to carbon usuallygraphite-electro5es; in which application there are certain peculiaradvantages referred tohereinafter in detail.

We have discovered that, by cooling a i carbon or gra hite electrode, itmay be used in resistance urnaces and still avoid the introduction ofcarbonaceous matter mto the product; as for example in the process ofreive charge is used herein it means a charge of material which whencold is a non-conductor of electricity or substantially so, and

which becomes an effective conductor only when heated to a hightemperature, either to 1 fusion or to an approach to the fusing point.

We have discovered that, by cooling a car bon or graphite electrode. toa temperature considerably below that at which it would be otherwisemaintained by the heat of the bath, the electrode is protected fromattack by the material of the bath and of the charge, even though suchmaterial is of a very oxidizing nature such that it would rapidlyconsume the electrode if the latter were not so cooled. We have foundthat, by observing proper conditions in conducting the opera-.

tion, it is possible to almost entirely and in some cases entirelypreserve the carbon or graphite electrodes intact in a very oxidizingbath such as a mixture of metallic oxids. These discoveries are of valuefor the following reasons:Thoughthe idea of watercooling a metallicelectrode to a temperature such that it will not be attacked or meltedby the bath of an electric resistance furnace or electrolytic furnace isof great value and enables us to successfully operate rocesses where,without the water-cooling, t e mate rial of the electrodes wouldinevitably contaminate the product, the substitution of water-cooledcarbon or graphite electrodes for the cooled metallic electrodes,enables us toraccomplish the same result with less loss by cooling andwith greater immunity from possible damage to the electrode throughtemporary abnormal conditions in the furnace which may cause smallarcing between the electrodes and the bath. Such substitution is foundto be of special advantage in resistance furnaces where it is necessaryto maintain a very high temperature to accomplish the desired reactions.

By water-cooling the carbon electrode we are enabled to immerse it inthe most oxidizing slag or bath, such as molten mixtures of oxidesuitable for refining high carbon metals, without danger of reactionsbetween the electrode and bath and consequent carburization of theproduct.

We have maintained such a highly oxidizperature high enough for the bathto be suitably conductive, so that the current may be conducted from theelectrode to the hotter working portion of the bath.

By the working ortion of the bath we mean that part of t e bath remoteenough from the cooling effect of the electrodes to be maintained, byits resistance to the cur' rent, at a tem erature sufliciently high tobring about tie desired reactions. This working portion of the bat willin all cases be higher in temperature than the por tions surrounding theelectrodes.

De ending on the nature of the charge and the temperature at which thebath becomes suitably conductive', that portion of the bath in contactwith the electrode may be in some cases solid, in some cases molten, andin other cases passing through various de rees of astiness.

ere t e portion of the bath in contact with the electrode is reduced toa solid or pasty state by the cooling, it forms a conductive coating onthe electrode and becomes practically the working electrode connectingthe electrode proper to the working portion of the bath. In fact, it maybe found desirable in some cases to lower the temperature sufficientlyto form such a working electrode and thus perfectly protect theelectrode proper.

The process is adapted also to the electrol sis of molten electrolytes.

The accompanying drawings suitable apparatus.

Figure 1 is a longitudinal section through a resistance furnace, andFig. 2 is a horizontal section through the same. These figures show themethod of a plying the water cooling to rectangular bloc of graphiteacting as electrodes. Fig. 3 is an elevation of one of the electrodesillustratin the method of arranging the water pi es I igs. 4, 5, 6 and 7are views similar to Fig. 1 illustrating more or less diagrammaticallythe application of the improvement to other arillustrate rangements ofthe electrodes.

Referring to the furnace illustrated, A is the body or wall of thefurnace or lining, which may be made of chrome ore or other suitablematerial, depending on the nature of the char e. The wall is held inshape by an iron she I B. The bath in Figs. 1 and 2 occupies the oblongspace or chamber 0 between the two electrodes which, in the presentembodiment of the invention are composed of pencils 1) and blocks E. Asufficient quantity of the bath is maintained to be alwa s in contactwith the exposed ends of the e ectrodes.

For cooling the exposed end of the graphite electrode, water isconducted through the blocks E b first boring holes of the proper size,and t ese pipes are then connected to each other by a pipe H, and to thesupply and discharge pipes J and K, the pipes J and K being beyond thesides of the blockas illustrated. The block with its several pipesattached is then molded in place in the chrome ore lining. The watercirculating through the pipes E and G at the desired rate, reduces thetemperature to a point depending on the conditions and nature of theath.

An example of the application of the invention is the refining offerro-chrome, and in this case the bath consists of a refining slag ofchrome ore and lime, and the charge is the metal to be refined or amixture of same with ore or ore and lime. The bath is maintained atabout the level indicated, and the product (low carbon ferro-chrome)collects-in the bottom of the crucible. 'The resistance of thebath N tothe electric current is in this case the only source of heat. The sameprinciple may be applied to practically all types of electric resistancefurnaces. For example Fig. 4 is a diagram of a furnace in which only onepole, the carbon electrode D, is cooled, the other pole being themetallic product M itself. The cooling in this case is accomplished'bypassing water through admission and discharge pipes J and K, enteringthe hollow stem of the electrode so as to maintain this stem always fullof water. A larger graphite or carbon block E is used for the contactend of the electrode.

by using a number of electrodes of the same polarity in place of theelectrodes D E.

Fig. 5 illustrates the application of the invention to a common form ofdouble pole furnace. In this furnace the current enters the bath by oneof the electrodes D and leaves it b the other, instead of leaving it byametal ic connection with the product at the bottom as in Fig. 4. Inthis construction the current passes in part directly throu h thebath-and in part through the bath from one electrode to the product andthence to theother electrode, the division of current followin Ohms law.This type of furnace might a so have two or more electrodes of eachclarity, forming the type known as doub e )ole multiple eleetror e. Theelectrodes are shown inclined, but otherwise they do not difl' er fromthe carbon electrode of Fig. 4.

Fig. 6 is a diagram of a double pole furnace in which the electrodes areof hollow carbon, preferably graphite, and are cooled by a circulationof water through the metallic cores 0 which also form the electricalconnections. As indicated the electrodes are of opposite polarity, andthe current goes in part directly through the bath from electrode toelectrode and in part by Way of the metallic product. The sameconstruction might be used, only making both electrodes of the samepolarity and connecting the metal at the bottom with the opposite poleof the circuit. The advantage of this construction is that theelectrodes may be rotated when it is necessary to expose a fresh surfaceto the bath, and this feature makes it one of the best types of furnacefor the purose.

P Fi 7 shows a cored metal ring P through which a circulation of wateris maintained and a graphite ring D constituting the electrode andfitting accurately the metal ring which serves both to cool the graphitering and convey the current to it. This is a single ole furnace, themetal at the bottom of the ath constituting the other pole, and is avery practical form of furnace. ations will suffice to show that theinvention is applicable to all types of electric resistance furnaceswhere the resistance is a fluid oxid bath, or other fluid bath.

Though we have described with great particularity of detail certainembodlments of the invention, yet it is not to be understood that theinvention is limited to the particular embodiments disclosed. Variousmodifica- These varitions thereof may be made by those skilled in theart Without departure from the invention.

What we claim is I 1 The method which consists in treating in anelectric furnace a pyro-conductive charge by passing through it from acarbon electrode in contact with it a current sufficient to maintain thecharge molten, and cooling said electrode sufiiciently to protect itfrom attack by the portion of the charge in contact with it.

2. The method which consists in treating in an electric furnace apyroconductive charge by passing through it from a carbon electrode incontact with it a current sufficient to maintain the charge molten, andcooling said electrode sufficiently to cause a portion of the charge tobe chilled in a protective but conducting coating thereon, whereby suchchilled portion forms in'effect a new working electrode.

In witness whereof, we have hereunto signed our names in the presence oftwo subscribing witnesses.

FRANZ VON K-UGELGEN. GEORGE O. SEWARD; Witnesses GEO. T. LANCASTER,FRIEDR. voN KIDDER.

